I just want the simplest possible way for my Python script to ask "is the Python code which I just generated syntactically valid Python?"
I tried:
try:
import py_compile
x = py_compile.compile(generatedScriptPath, doraise=True)
pass
except py_compile.PyCompileError, e:
print str(e)
pass
But even with a file containing invalid Python, the exception is not thrown and afterwards x == None.
There is no need to use py_compile. It's intended use is to write a bytecode file from the given source file. In fact it will fail if you don't have the permissions to write in the directory, and thus you could end up with some false negatives.
To just parse, and thus validate the syntax, you can use the ast module to parse the contents of the file, or directly call the compile built-in function.
import ast
def is_valid_python_file(fname):
with open(fname) as f:
contents = f.read()
try:
ast.parse(contents)
#or compile(contents, fname, 'exec', ast.PyCF_ONLY_AST)
return True
except SyntaxError:
return False
Be sure to not execute the file, since if you cannot trust its contents (and if you don't even know whether the file contains valid syntax I doubt you can actually trust the contents even if you generated them) you could end up executing malicious code.
py_compile is also a standard library.
ast.parsewould raise an exception during parsing an invalid Python code.astmodule'sparsefunction. In fact there is acompilebuilt-in function that can be used to do that.